docs: def _stub_tag(constructor, node):
      """Stub a constructor with a dictionary."""
      seen = getattr(constructor, "_stub_seen", None)
  
      if seen is None:
          seen = constructor._stub_seen = set()
  
      if node.tag not in seen:
          print("YAML tag {} is not supported".format(node.tag))
          seen.add(node.tag)
  
      return {}